MJ Ray wrote:
ISP forums, router forums, http://www.ispreview.co.uk/talk/ http://www.thinkbroadband.com/ http://www.broadband-help.com/forums/
When I've looked at those in the past they've all seemed a bit too consumer-level, and I don't want to go through several more rounds of checking filters etc unless there's a specific reason to think that they might be causing our specific problem. (Not least because the end user is fast running out of patience and getting him to try apparently random and pointless changes at this stage will push him over the edge!) I'll look again at the above and see which looks most likely to be able to go to a technical level quite quickly.
Both BT-based or Local Loop Unbundled? Which ISPs?
I believe both BT based, not LLU. Certainly the current ISP (Enta) is BT-based. This has the advantage that I can see the BT fault reports on the account directly and can pass information back at a technical level rather that dealing with end-user facing tech support.
I'd put a Linux-based router in there (yay back on topic) and get decent debugging information out of it to see where to point the finger.
I've lost track of which router they've got but we usually use Linux-based ones. Unfortunately the customer isn't local (Chipping Norton), and getting information remotely isn't easy. I would just go to site if I thought that would help, but realistically it would mean running some tests, handing the results back to BT, waiting, then going back a day or too later to run some more tests.
I might see if I can configure a router using RouterTech firmware to generate suitable logs and then send it to them to swap in, that way I'd only need to talk them through viewing the logs after the connection is up.
Look at the ADSL negotiation, the various line stats (SNR, attenuation, and so on) and watch the PPP negotiations by starting pppd from the commandline with the debug option or sending it a USR1 signal (which toggles the debug option) soon after start.
Good things to try, I'm just going to have to see if I can find a way to do them remotely! I can try most of them on our spare ADSL line in the office though.